This invention relates generally to ultrasonic transducers, and more particularly, to an ultrasonic transducer arrangement having a matrix of ultrasonic oscillators.
Ultrasonic arrays, illustratively of the type used in medical diagnostic equipment, are configured from a relatively large oscillator slab which is then electrically or mechanically subdivided to produce groups of individual oscillators, which may be arranged in a linear configuration. Electrical subdivision is achieved by applying separate electric contact areas, generally in the form of a surface metallization, in regularly arranged rectangular zones. Once the oscillator groups have been formed, the oscillator material is polarized by the electric contact areas, which are provided with electric leads. The transducer elements are then arranged between a damper body and a matching body.
One known transducer comb for an ultrasonic transducer array is known as the compound scanner type, and is formed of a linear arrangement of ultrasonic oscillators. The ultrasonic oscillators can be subdivided into acoustically and mechanically separated transducer elements, by fine subdivision techniques, the separated transducer elements being connected electrically in parallel in groups which are controlled simultaneously. It is generally desirable to keep the width of the transducer elements substantially less than one half of the wave length (.lambda./2) of the radiated or received ultrasound waves. German Pat. No. 28 29 570 teaches a matrix of transducer elements of the type described hereinabove having additional transverse gaps.
In ultrasonic transducer arrangements of the type which are finely subdivided by mechanical operations, the spacing between the transducer elements, which is determined by the width of the mechanical cut, cannot be made arbitrarily small. As the width of the transducer elements themselves is decreased, the losses which result from the subdivision operation increase because the size of the spaces between the transducer elements approaches the size of the transducer elements themselves. Such losses are further increased if a matrix of transducer elements is produced with additional transverse subdivision. As a result of their mechanical separation, the transducer elements do not produce a form-locking structural unit, and therefore, electrical contacts are expensive to apply to arrangements having many transducer elements.
It is, therefore, an object of this invention to provide a matrix of ultrasonic oscillators which have a large number of transducer elements having very small widths and small spacing therebetween, which forms a mechanically strong structural unit and which can be contacted and controlled in a simple manner so as to permit electronic focusing and variable aperture.
Ultrasonic arrays used in mechanical diagnostics are provided with B-displays for preparing sectional images. Such ultrasonic arrays are provided with a mechanical focus arrangement in the longitudinal direction of the ultrasonic array, and an electronic focus in the direction perpendicular to the longitudinal. The electronic focus can be moved in depth (i.e., parallel to the direction of radiation) by controlling the excitation of the oscillators in a group. Such focusing, however, cannot be achieved with a mechanical focusing arrangement which may be formed, for example, by a cylindrical curvature of the radiating surface. A substantial technological effort would be required to achieve the advantages of electronic focusing in the direction where only mechanical focusing is available.